1. Field of the Invention
The present invention relates to a pigment dispersion composition having a good dispersibility and a good transparence, with such excellent anti-coating properties that the composition does not have an adverse influence on other materials, i.e. soaking into other coatings. The present invention further discloses a display apparatus such as a cathode ray tube and a method of manufacturing the apparatus.
2. Description of the Related Art
A color cathode ray tube is an example of a display apparatus for displaying an image by using emitting light from a phosphor layer. Conventionally, various methods for improving the contrast or color purity of such a display device have been proposed.
For example, Jpn. Pat. Appln. KOKAI Publications Nos. 48-17263, 52-63060 and 64-7457 each disclose a method in which a pigment layer having the same color as that of the emitting color from the phosphor layer is provided between the face plate and the phosphor layer.
Further, Jpn. Pat. Appln. KOKAI Publication No. 52-77578 discloses a method of forming a pigment layer by adding a pigment into a pre-coating solution before the phosphor layer is applied. Jpn. Pat. Appln. KOKAI Publications Nos. 53-69577 and 56-160746 each mention a method of embedding phosphor particles into a pigment layer which was made sticky.
Jpn. Pat. Appln. KOKAI Publication No. 53-65654 discloses that a phosphor screen is formed by forming a pigment layer containing a binder in the inner surface of a panel and then applying a phosphor suspension containing a photo-sensitive binder on the pigment layer, thereafter exposing the suspension to light and developing.
However, the above-described methods entail the below-described drawbacks, and therefore it is difficult to actually employ such a phosphor film having a pigment filter layer. First, the transparence of the pigment layer is insufficient, and the performance of the filter is poor, thus making it not possible to achieve good contrast properties. Second, the method involves a limited condition for work, and therefore defect-free filter layers cannot be constantly obtained.
According to the method of manufacturing a phosphor screen disclosed in Jpn. Pat. Appln. KOKAI Publication No. 64-7457, the pigment layer is formed by the slurry method, and after a while, the phosphor layer is formed by further using the slurry method. As a result, the number of the steps involved is twice as many as a general method, and the production cost is increased.
The present invention has been proposed in consideration of the drawbacks of the conventional techniques.
The first object of the invention is to provide a pigment dispersion composition having a good dispersibility and a good transparence, with such excellent anti-coating properties that the liquid composition does not have an adverse influence on other materials, i.e. soaking into other coatings.
The second object of the invention is to provide a display apparatus including a phosphor screen with a filter by using a pigment dispersion composition. The phosphor screen has a pigment layer with the same color as the emitting color from each phosphor layer. The pigment layer is located between the face plate and the phosphor layer and has a good transparence, and a good filter performance. This means that light emitted from phosphor can be transmitted through the filter while the other light can be absorbed in the filter.
The third object of the invention is to provide a method of manufacturing a display apparatus including a phosphor screen with a filter, using a pigment dispersion composition, having good transparence, a good filter performance, and contrast properties. This method which does not allow color contamination, is easily accomplished at a low cost.
The pigment dispersion composition of the present invention has a good dispersibility and anti-coating properties. A high dispersibility indicates good filter properties, and an excess pigment dispersion composition applied to an undesired part in the patterning step can be easily removed. When the anti-coating properties are good, high filter properties can be obtained. This is because, the pigment dispersion composition does not seep out into the phosphor layer.
When the pigment dispersion composition is used in, the display device of the present invention, improved a brightness, contrast characteristics and color purities are obtained.
Because, the pigment dispersion composition has good anti-coating properties, it is not necessary to add a photoresistor. Consequently, with the method of the present invention, another coating layer containing the photoresist can be formed on a coating layer of the pigment dispersion composition without the just mention treatment. Therefore, it only suffices that a patterning is performed on the photoresist-containing layer, so as to pattern the photoresist-containing layer together with the coating layer of the pigment dispersion composition. In the case where the photoresist-containing layer also contains phosphor, a phosphor layer can be formed by performing a development process and an exposure step. Thus, according to the present invention, the manufacturing steps can be facilitated without deteriorating the filter effect of the pigment layer, or the light emitting efficiency of the phosphor layer.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.